It is well known that the microstructural and related mechanical property changes for binary alloy systems can be influenced by temperature treatment. This is especially true in cases in which the composition sought to be affected displays a miscibility gap over some range of composition distribution. For purposes of this invention, the miscibility gap of a given binary alloy is that region where, for a given temperature and composition, the two components are not fully miscible with each other. Moreover, in the miscibility gap, each component exists in a stable form. That is to say, a two-phase field exists.
It is well documented in the literature that several platinum-based binary alloy systems have confirmed miscibility gaps. Some examples of these binary alloy systems include: Au--Pt, Pd--Pt, Pt--Ir, and Pt--Rh. It is also well documented in the literature that the mechanical properties for these alloy systems are dependent upon the method by which the alloys are worked. For example, cold-work, strain hardening results in increased tensile strength but reduced ductility, and short term heat treatment results in increased ductility but reduced tensile strength.
An example of a process combining several process steps is disclosed in U.S. Pat. No. 5,084,108 to Kretchmer. This patent discloses a method for forming compression spring gemstone mountings wherein a heat-treatable metal is annealed and heat treated to increase the yield strength. The method disclosed, however, results in an increase to Vickers hardness (specified as an increase in both strength and elastic behavior) and a corresponding reduction in ductility (plastic behavior).